M. B. Panish

JUNCTION LASERS WHICH OPERATE CONTINUOUSLY AT ROOM TEMPERATURE

Double‐heterostructure GaAs–Alx Ga1−x As injection lasers which operate continuously at heat‐sink temperatures as high as 311°K have been fabricated by liquid‐phase epitaxy. Thresh‐olds for square diodes as low as 100 A/cm2 and for Fabry‐Perot diodes as low as 1600 A/cm2 have been obtained. Some details of preparation and properties are given.

Low‐temperature photoluminescence from InGaAs/InP quantum wires and boxes

InGaAs/InP quantum well layers grown by gas source molecular beam epitaxy have been used to fabricate quantum wires and boxes with transverse dimensions as small as ∼300 A. These artificial structures exhibit intense low‐temperature photoluminescence and show exciton shifts of 8–14 meV expected of low dimensional confinement. Low surface recombination velocity characteristic of InP and its alloys should allow luminescence studies of features as small as ∼30 A under moderate excitation intensities.

Refractive index of AlxGa1−xAs between 1.2 and 1.8 eV

The refractive indices of AlxGa1−xAs samples prepared by liquid‐phase epitaxy were determined from accurate double‐beam reflectance measurements. The variation of the refractive index with photon energy at room temperature was obtained for AlAs mole fractions between 0 ≤ x ≤ 0.38 in the spectral range 1.2–1.8 eV.

Temperature Dependence of the Energy Gap in GaAs and GaP

Absorption measurements from 300°–973°K for GaAs and to 1273°K for GaP were made in order to determine the energy gap Eg of these materials at high temperatures. These data, together with previously published results, show that the energy‐gap width may be represented by a simple expression for all temperatures. As a function of the absolute temperature T, the direct gap in GaAs is given by Eg=1.522−5.8×10−4T2 / (T+300) eV, and the indirect gap in GaP is given by Eg=2.338−6.2×10−4T2 / (T+460) eV. The general form of the expression for the energy gap is Eg=Eg(0)−aT2 / (T+β), where Eg(0) is the energy gap at 0°K, β is approximately the 0°K Debye temperature, and a is an empirical constant.

Subpicosecond InP/InGaAs heterostructure bipolar transistors

Bipolar transistors with subpicosecond extrinsic delay are discussed. These InP/InGaAs heterostructure transistors show a unity-current-gain cutoff frequency f/sub

GaAs–AlxGa1−xAs Double Heterostructure Injection Lasers

/T=165 GHz and maximum oscillation frequency f/sub MAX/=100 GHz at room temperature. The authors model shows that an f/sub

Composition Dependence of the Ga1−xAlxAs Direct and Indirect Energy Gaps

/T beyond 386 GHz is obtainable by further vertical scaling. Ring oscillators implemented with nonthreshold logic (NTL) and transistors having f/sub MAX/=71 GHz show a propagation delay of 14.7 ps and 5.4 mW average power consumption per stage.<<ETX>>

Mode Reflectivity and Waveguide Properties of Double‐Heterostructure Injection Lasers

Double heterostructure GaAs–AlxGa1−xAs junction lasers which have very low thresholds and which have been operated continuously at and above room temperature have been fabricated by liquid phase epitaxial growth. The threshold current density of these lasers decreases approximately linearly with the thickness of the active region from 3 to at least 0.5 μm. This is interpreted as the result of near perfect carrier and optical confinement as the result of large steps in the energy gap and index of refraction at the heterojunctions in these diodes. The gain in these lasers is very high and its dependence upon current density is superlinear. Loss is very low and almost that expected from free carriers. Complete polarization of the lasing mode was observed. This latter is interpreted to be the result of an increased reflection coefficient for the T E mode.

DOUBLE‐HETEROSTRUCTURE INJECTION LASERS WITH ROOM‐TEMPERATURE THRESHOLDS AS LOW AS 2300 A/cm2

Photoresponse measurements were made to determine the compositional dependence of the Ga1−xAlxAs direct Γ15→Γ1 and indirect Γ15→X1 energy gaps. These data, together with other information, show that the crossover composition and energy gap are between 0.35<xc<0.40 and 1.87<Egc<1.97 eV, and that the most resonable values are 0.37 and 1.92 eV.

Measurement of heterojunction band offsets by admittance spectroscopy: InP/Ga0.47In0.53As

It is shown that the mirror reflectivity for tightly confined planar waveguide modes becomes a function of both the waveguide and mode parameters. This dependence of the mirror reflectivity plays the dominant role in the selection of the oscillating transverse modes and explains why room‐temperature cs‐type double‐heterostructure lasers tend to lase in higher‐order TE modes. Experimental investigations show that the waveguide and mode parameters are qualitatively consistent with a dielectric step waveguide which is mainly perturbed by small gradients of the optical dielectric constant arising from impurity segregation.